Robert W. Shields

Functional anatomy of the autonomic nervous system.

Summary: The autonomic nervous system (ANS) via its sympathetic and parasympathetic divisions influences the function of nearly all organ systems. Via autonomic reflexes, the ANS is responsible for maintaining homeostasis of the internal environment. This is achieved by a rather complex integration of autonomic sensory information, somatic sensory information, and descending influences from higher central nervous system centers.

STRENGTH TRAINING CAN IMPROVE STEADINESS IN PERSONS WITH ESSENTIAL TREMOR

We evaluated the effect of a strength‐training program on the ability of persons with essential tremor to exert steady forces with the index finger. Thirteen subjects with a diagnosis of essential tremor were assigned to three different groups: one group trained with heavy loads, one with light loads, and one did not perform any training. Subjects attempted to generate steady contractions during both postural and constant‐force tasks. Steadiness was quantified by the root mean square amplitude of acceleration during postural tasks and the standard deviation and coefficient of variation of force during the constant‐force tasks. Subjects who performed the training program with heavy loads experienced an increase in steadiness around the target force during the constant‐force tasks. Subjects in the other two groups did not exhibit any changes. These findings suggest that strength training can decrease the magnitude of tremor. However, we did not observe any associated improvements in functional abilities.

Phrenic neuropathy due to neuralgic amyotrophy

The authors reviewed the medical records of 33 patients diagnosed with idiopathic phrenic neuropathy and found that 17 patients had clinical features of neuralgic amyotrophy. They concluded that a careful clinical and electrodiagnostic evaluation may implicate neuralgic amyotrophy as a causative disease in patients with apparently isolated phrenic neuropathy.

Compartment syndromes and compression neuropathies in coma

Eight patients are reported who developed peripheral nerve injuries due to limb compression during unattended coma. In each patient, the site of the peripheral nerve lesion or the unique combination of peripheral nerve lesions and swollen limbs, pressure blisters, or myoglobinuria indicated that compartment syndromes caused the nerve injury. The peripheral nerve injuries were characterized by severe axonal loss with persistent and often disabling sequelae.

Laryngeal nerve function after total laryngeal transplantation.

The first successful composite human laryngeal transplantation was performed by a team led by the senior author on January 4, 1998. The recipient was a 40-year-old male who had sustained a crush injury to his larynx 20 years prior, rendering him aphonic. Multiple previous attempts for reconstruction at an outside hospital were unsuccessful. The donor was a 40-year-old male who had died from a ruptured cerebral aneurysm. The specifics of the procedure have been detailed elsewhere. 1 Throughout the patients postoperative course, serial fiberoptic evaluations and voice testing were performed to evaluate laryngeal reinnervation reflected in phonatory function. We herein report the results of these exams, as well as the results of electromyographic recordings of the laryngeal musculature 4 years posttransplantation.

ELECTRODIAGNOSTIC FEATURES OF TRUE NEUROGENIC THORACIC OUTLET SYNDROME

Introduction: We report the electrodiagnostic (EDX) features of 32 patients with surgically verified true neurogenic thoracic outlet syndrome (TN‐TOS). Methods: Retrospective record review. Results: We found uniform EDX evidence of a chronic axon loss process that affected the lower portion of the brachial plexus and disproportionately involved the T1 more than the C8 sensory and motor fibers. Because of this relationship, the medial antebrachial cutaneous sensory nerve (T1) and median motor (T1 > C8) study combination was abnormal in 89%, whereas response combinations that primarily assessed the C8 fibers were less frequently affected. Conclusions: The characteristic EDX features of TN‐TOS are T1 > C8 nerve fiber involvement. A comprehensive EDX examination of the lower plexus with contralateral comparison studies is imperative to diagnose this disorder accurately. Muscle Nerve 49: 724–727, 2014

Single‐fiber electromyography is a sensitive indicator of axonal degeneration in diabetes

Axonal degeneration with reinnervation was assessed in diabetic subjects with single-fiber electromyography (SF-EMG). SF-EMG was performed on 18 control subjects, 20 diabetic control subjects without clinical or electromyographic evidence of polyneuropathy, and 30 diabetic subjects with clinical and electromyographic features of polyneuropathy. In the diabetic controls and diabetic neuropathy subjects, fiber density and jitter were increased indicating axonal degeneration with reinnervation. These findings confirm that axonal degeneration is a principal pathologic mechanism in diabetic polyneuropathy and that axonal degeneration commonly occurs in asymptomatic diabetic subjects. SF-EMG is thus a sensitive method for assessing axonal degeneration in diabetic subjects.

Neuralgic amyotrophy precipitated by Epstein–Barr virus

Neuralgic amyotrophy (NA), or Parsonage–Turner syndrome, is an uncommon idiopathic disorder that occurs on a sporadic or hereditary basis. We describe the clinical and electrodiagnostic (EDX) features of NA in two siblings with documented Epstein–Barr virus (EBV) infections. This raises the possibility that a common infection may trigger NA in family members who possess a genetic disposition to this disease. Patient 1, a 20-year-old right-handed man, presented with fever, night sweats, and fatigue followed by aching pain in the right elbow and left shoulder. On day 11, he developed weakness in bilateral shoulder elevation, forearm pronation, right thumb flexion, right finger flexion, left wrist extension, and patchy sensory loss. The table contains laboratory and imaging results. IV solumedrol (900 mg/day for 3 days) did not provide relief. His weakness and pain continued to progress over 2 months, and a trial of IV immunoglobulin (IVIG; 400 mg/kg/day for 5 days) resulted in dramatic relief of pain. An EDX examination on day 62 showed evidence of severe to apparently complete …

Contraction patterns of intrinsic laryngeal muscles induced by orderly recruitment in the canine.

The specific performance of intrinsic laryngeal muscles has been difficult to evaluate, especially in living subjects. To reproduce natural contractions, we artificially induced orderly recruitment of their innervating axons according to the size principle. In 5 dogs, both recurrent laryngeal nerves(RLNs) were stimulated with 50 through 10 Hz, 300 to 1000 μA currents while 600 Hz, 1000 to 0 μA decreasing blocking currents were administered. Surface electromyography electrodes placed on the thyroarytenoid, posterior cricoarytenoid, and lateral cricoarytenoid muscles were used to determine the amplitudes (in mA) of compound muscle action potentials. There was a highly statistically significant difference (P<.004) between the thyroarytenoideus which had the fastest rate of recruitment (8.38%), and posterior cricoarytenoideus, which had the slowest (4.81%). There was an intermediate recruitment rate (6.72%) of the lateral cricoarytenoideus, a divergence attributed to a more equal distribution in fast and slow types of myofibers and a smaller sample. We submit that RLN axons can be recruited in an orderly manner according to their sizes and that the rates are unique to the muscle classes they innervate. The parameters defining these contraction patterns may offer key information for laryngeal pacing.

Tentorial dural arteriovenous fistula presenting with quadriparesis: case report and review of the literature.

Tentorial dural arteriovenous fistulas (TDAVFs) draining into the spinal venous system are rare lesions. The clinical presentation can be devastating and the diagnosis delayed because of the initial nonspecific imaging and laboratory findings. We report a case of a 20-year-old woman with a rapidly progressive myelopathy, who was found to have a left TDAVF, fed by a single arterial feeder with drainage into the perimedullary venous system. The fistula was surgically clipped. The patient showed neurologic improvement at her 3-month follow-up but still had significant weakness of all 4 extremities. Early diagnosis is key as the neurologic symptoms are reversible with appropriate treatment. We review the relevant literature, imaging characteristics, and treatment modalities for TDAVF.